JP6514904B2 - Optical semiconductor device - Google Patents

Description

  The present invention relates to an optical semiconductor device.

  In recent years, an optical functional device on a silicon substrate using silicon electronic circuit manufacturing technology that is inexpensive and capable of large-scale integration has attracted attention. In response to the increase in computing capacity required for high-performance servers, supercomputers, etc., higher performance has been achieved by making the CPU (Central Processing Unit) multi-core or the like. On the other hand, in communication between chips and boards, communication with electrical signals is reaching its limit due to the problem of physical distance with respect to high-speed computing capability. An optical communication element formed on a large-scale silicon substrate based on a low loss and small silicon wire waveguide, so-called silicon photonics solves the problem of communication capacity shortage of such high-speed information processing equipment It is expected as a technology. Among them, the application of Wavelength Division Multiplexer (WDM) technology, which has been put to practical use for communication applications, to silicon photonics is expected to be effective in increasing transmission capacity and reducing optical cables, and research and development is being promoted widely .

  In the optical transceiver using silicon photonics, the optical transmitter unit comprises a light source, an optical modulator, etc., and the optical receiver unit comprises a photodetector etc. As a photodetector in silicon photonics, for example, there is a photodetector composed of a waveguide type p-i-n-type Ge photodiode as disclosed in Non-Patent Documents 1 and 2.

J. Fujikata et al., "Si Waveguide-Integrated Metal-Semiconductor-Metal and p-i-n-type Ge Photodiodes Using Si-Capping Layer", Jpn. J. of App. Phys., 52, 04CG10-1-5, 2013. T. Y. Liow et al., "Silicon Modulators and Germanium Photodetectors on SOI: Monolithic Integration, Compatibility, and Performance Optimization", IEEE J. of Selected Topics in Quantum Electoronics, Vol. 16, No. 1, 2010. Lucas B. Soldano and Erik C. M. Pennings, JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 13, NO. 4, APRIL 1995.

  Since the optical receiver unit is required to be compact and to speed up communication, the waveguide type photodetector as described above is also required to be compact and have high-speed response.

According to one aspect of the present embodiment, the input optical waveguide formed on the substrate, the detector unit to which the input optical waveguide is connected on one side, and the detector unit on the one side And a reflective film formed on the other end face facing the other, wherein the detector detects light input from the input optical waveguide, and the input optical waveguide is the detector. is connected to a central portion of one side of the, while the light input to the side of the detector unit from the input optical waveguide is reflected by the reflective film formed on the end surface of the other side, the in one side of the detector unit, and wherein the imaging to Rukoto each image on both sides of a region where the input optical waveguide is connected.

  According to the disclosed optical semiconductor device, the optical semiconductor device can be miniaturized, and the response can be made faster.

Explanation of optical semiconductor device Explanatory drawing of the optical semiconductor element in 1st Embodiment Illustration of 1 × 2 MMI waveguide An illustration of a reflective MMI photodetector Process diagram (1) of manufacturing method of optical semiconductor device in the first embodiment Process drawing (2) of manufacturing method of optical semiconductor device in the first embodiment Process drawing (3) of manufacturing method of optical semiconductor device in the first embodiment Process drawing of the manufacturing method of the optical semiconductor element in 1st Embodiment (4) Step diagram of manufacturing method of optical semiconductor device in the first embodiment (5) Step diagram of manufacturing method of optical semiconductor device in the first embodiment (6) Process drawing of manufacturing method of optical semiconductor device in the first embodiment (7) Process drawing of manufacturing method of optical semiconductor device in the first embodiment (8) Process drawing of manufacturing method of optical semiconductor device in the first embodiment (9) Step diagram of manufacturing method of optical semiconductor device in the first embodiment (10) Step diagram of manufacturing method of optical semiconductor device in the first embodiment (11) Step diagram of manufacturing method of optical semiconductor device in the first embodiment (12) Explanatory drawing of the optical semiconductor element in 2nd Embodiment Process diagram (1) of manufacturing method of optical semiconductor device in the second embodiment Process drawing of the manufacturing method of the optical semiconductor element in 2nd Embodiment (2) Step diagram of manufacturing method of optical semiconductor device in the second embodiment (3) Step diagram of manufacturing method of optical semiconductor device in the second embodiment (4) Step diagram of manufacturing method of optical semiconductor device in the second embodiment (5) Process diagram of manufacturing method of optical semiconductor device in the second embodiment (6)

  A mode for carrying out will be described below. In addition, about the same member etc., the same code | symbol is attached | subjected and description is abbreviate | omitted.

First Embodiment
First, the structure of a typical waveguide-type p-i-n-type Ge photodetector will be described based on FIG. 1 (a) is a top view of the photo detector, FIG. 1 (b) is a cross-sectional view cut along a dashed dotted line 1A-1B in FIG. 1 (a), and FIG. A cross-sectional view taken along a dashed-dotted line 1C-1D in FIG.

  Such a waveguide-type p-i-n-type Ge photodetector is expected as a highly sensitive photodetector because it has a high absorption coefficient for signal light in the 1.55 μm band. However, the waveguide type photodetector is usually required to be miniaturized because the element length is required to a certain extent in order to sufficiently absorb the signal light, and high speed response is required due to the demand for high speed communication and the like. Sex is required.

The photodetector having the structure shown in FIG. 1 is manufactured using an SOI (Silicon on Insulator) substrate. In the SOI substrate, a BOX layer 912 and a p ⁻ -Si layer 920 are stacked on a Si substrate 911. ^P up to the region p-side electrode 942 is formed from the photodetector unit - to -Si layer 920, p-Si region 921 is formed by doping an impurity element to be a p-type. An i-Ge layer 930 is formed in a central portion above the p-Si region 921, and an n-Ge region 931 is doped on the upper portion of the i-Ge layer 930 by doping an impurity element that becomes an n-type. Is formed. An n-side electrode 941 is formed of Al on the n-Ge region 931, and on the p-Si region 921 exposed on both sides of the region where the i-Ge layer 930 is formed, The p-side electrode 942 is formed of Al. Further, except for the portion where the n-side electrode 941 and the p-side electrode 942 are formed, the top of the p-Si region 921 and the i-Ge layer 930 etc. is covered by a cladding layer 950 formed of SiO ₂ . . The photodetector portion is formed of a p-Si region 921, an i-Ge layer 930, and an n-Ge region 931, and the photodetector portion is an input optical waveguide 960 formed by processing the p ⁻ -Si layer 920. Is connected. The light input from the input optical waveguide 960 is absorbed and detected in the i-Ge layer 930 in the photodetector section.

  The i-Ge layer 930 and the n-side electrode 941 in the photodetector portion are formed in a substantially rectangular shape having a length in the longitudinal direction of about 30 μm and a length in the lateral direction of about 10 μm. The input optical waveguide 960 is connected to the central portion of one of the sides in the opposite short direction. In the waveguide type photodetector having the structure shown in FIG. 1, as described above, miniaturization and high-speed response are required.

(Optical semiconductor device)
Next, a waveguide type photo detector which is an optical semiconductor device according to the present embodiment will be described based on FIG. 2 (a) is a top view of the optical semiconductor device according to the present embodiment, and FIG. 2 (b) is a cross-sectional view taken along the dashed dotted line 2A-2B in FIG. 2 (a). c) is a cross-sectional view cut along a dashed-dotted line 2C-2D in FIG.

The optical semiconductor element in the present embodiment is manufactured using an SOI substrate. In the SOI substrate, a BOX layer 12 made of SiO ₂ (silicon oxide) and a p ⁻ -Si layer 20 are stacked on a Si (silicon) substrate 11. P up to the region p-side electrode 42 is formed from the photodetector unit ^- to -Si layer 20, p-Si region 21 is formed by doping an impurity element to be a p-type. An i-Ge (germanium) layer 30 is formed in the central portion above the p-Si region 21, and the upper portion of the i-Ge layer 30 is doped with an n-Ge impurity element to be an n-type. Region 31 is formed. An n-side electrode 41 is formed of Al on the n-Ge region 31, and a p-side electrode 42 of Al is formed on the p-Si region 21 exposed on both sides of the i-Ge layer 30. Is formed. Further, except for the region where the n-side electrode 41 and the p-side electrode 42 are formed, the p ^-- Si layer 20 and the i-Ge layer 30 etc. are covered by the cladding layer 50 formed of SiO ₂ (silicon oxide). It is

  The i-Ge layer 30 in the detector portion is formed to have a substantially rectangular shape with a width W and a length L. The input optical waveguide 60 is connected to one side 30a of the detector portion corresponding to one side of the two sides of the substantially rectangular i-Ge layer 30 which have the width W, and corresponds to the other side. An end surface 70 is formed on the other side 30 b of the detector unit. In addition, a reflection film 71 is formed on the end surface 70 of the other side 30 b of the detector portion.

Input optical waveguide ^60, p - is formed by processing the -Si layer 20, at one central portion of the side 30a of the detector portion, under i-Ge layer 30 ^p - connected to -Si layer 20 It is done. Further, on the other side 30b of the detector portion, the n-Ge region 31, the i-Ge layer 30, the p-Si region 21, the p ^-- Si layer 20, the BOX layer 12, and part of the Si substrate 11 are dry etched. The end face 70 is formed by removing by the like. In the present embodiment, the reflective film 71 is formed by forming a dielectric multilayer film so as to cover the end face 70 formed on the other side 30 b of the detector section.

Therefore, light incident on one side 30 a of the detector from the input optical waveguide 60 propagates through the i-Ge layer 30 and the p ⁻ -Si layer 20 while being absorbed in the i-Ge layer 30, and the other of the detector The light is reflected by the reflection film 71 at the end face 70 of the side 30b of the The light reflected by the reflective film 71 propagates through the i-Ge layer 30 and the p ^-- Si layer 20 while being absorbed again by the i-Ge layer 30, and then, at one side 30a of the detector portion, the input optical waveguide The region where 60 is connected forms an image in a different region. Specifically, by setting the length L between one side 30a and the other side 30b to a predetermined length, the area where the input optical waveguide 60 is connected on one side 30a of the detector section The light reflected by the reflective film 71 can be imaged in an area different from In the present embodiment, for the length L between one side 30a and the other side 30b in the detector section, the light reflected by the reflective film 71 is connected to the input optical waveguide 60 on one side 30a. The image is formed in such a length that an image is formed at two places on both sides of the area.

  As described above, the light reflected by the reflection film 71 is imaged on an area different from the area to which the input optical waveguide 60 is connected on one side 30 a of the detector unit, thereby forming the light on the input optical waveguide 60. It is possible to prevent return light from entering. When return light is incident on the input optical waveguide 60, when the light source connected to the input optical waveguide 60 is a laser light source, the laser oscillation in the light source becomes unstable, which is not preferable.

  Next, a method of forming an image by light reflected by the reflective film 71 in a region different from the region to which the input optical waveguide 60 is connected on one side 30 a of the detector unit will be described.

  FIG. 3 shows the structure of a 1 × 2 MMI (Multi-Mode Interferometer) waveguide to explain the above contents. In this 1 × 2 MMI waveguide 110, one input optical waveguide 120 is connected to the central portion of one side 110a, and two output optical waveguides 131 and 132 are connected near both ends of the other side 110b. It is done. In the 1 × 2 MMI waveguide 110, the signal light input from the input optical waveguide 120 is separated into a plurality of propagation modes, and while forming an image at a specific point by inter-mode interference, the 1 × 2 MMI waveguide 110 is formed. To propagate. Therefore, by forming the output optical waveguides 131 and 132 at the imaging positions of the two images on the other side 110b, it is possible to obtain a 1 × 2 branch. That is, the two output optical waveguides 131 and 132 are incident from the input optical waveguide 120 connected to one side 110a, and the light propagated in the 1 × 2 MMI waveguide 110 is on the other side 110b. They are respectively formed at two positions for imaging. Thus, the 1 × 2 MMI waveguide 110 is obtained by setting the length from one side 110 a to the other side 110 b of the 1 × 2 MMI waveguide 110 to a desired length Lm. Thus, light incident from the input optical waveguide 120 on one side 110 a of the 1 × 2 MMI waveguide 110 is branched into two at the output optical waveguides 131 and 132 on the other side 110 b and output.

  FIG. 4 shows a structure in which a reflective film is formed by cutting a 1 × 2 MMI waveguide at a central portion. Specifically, the input optical waveguide 120 is connected to the central portion of one side 111 a of the MMI waveguide portion 111, and the reflective film 140 is formed on the other side 111 b. The length from one side 111 a to the other side 111 b in the MMI waveguide portion 111 is formed to be Lm / 2. Thereby, light incident from the input optical waveguide 120 connected to one side 111 a of the MMI waveguide portion 111 propagates the MMI waveguide portion 111 toward the other side 111 b and is formed on the other side 111 b It is reflected by the reflected film 140. The light reflected by the reflective film 140 propagates toward one side 111a, and on one side 111a, an image is formed at two places on both sides of the region to which the input optical waveguide 120 is connected. This is formed such that the length from one side 111 a to the other side 111 b in the MMI waveguide section 111 is Lm / 2, and light incident from the input optical waveguide 120 is reflected by the reflective film 140. This is because the optical path length until it returns to one side 111a again is Lm. For this reason, light incident on the MMI waveguide portion 111 from the input optical waveguide 120 is reflected by the reflective film 140, and an image is formed in an area different from the area to which the input optical waveguide 120 is connected on one side 111a. It is an image.

In the optical semiconductor device of the present embodiment, the signal light is input light, p ^- from the input optical waveguide 60 formed by -Si layer 20, the region in which the detector unit is formed p ^- -Si layer 20 , And are evanescently coupled to the i-Ge layer 30 having a higher refractive index than the p ^-- Si layer 20, and propagate while decaying in the i-Ge layer 30.

As described above, the signal light is reflected by the reflection film 71 formed on the other side 30b opposite to the one side 30a of the detector unit to which the input optical waveguide 60 is connected. Therefore, in the MMI waveguide, the signal light is separated into a plurality of propagation modes, interferes with each other, and forms an image at a specific point. The imaging point is expressed by the following equation 1. Here, N is the number of images to be formed, and _Lπ is the beat length of the MMI waveguide.

Further, the beat length _Lπ is expressed by the following equation 2. Here, W _e is the effective width of the MMI waveguide, n _r is the equivalent refractive index of the MMI waveguide, and λ ₀ is the wavelength of the signal light in vacuum.

Also, the effective width W _e of the MMI waveguide is expressed by the formula shown in Formula 3 below. Here, W _M is the physical width of the MMI waveguide, and n _c is the refractive index of the cladding. Further, σ is 1 when the signal light is TE polarization, and 0 when it is TM polarization.

The optical semiconductor device in the present embodiment is a reflective MMI photodetector based on the above-described MMI waveguide concept. In the optical semiconductor device according to the present embodiment, the detector for detecting light is formed of the p ⁻ -Si layer 20 and the i-Ge layer 30 formed of the SOI substrate, and the wavelength of the signal light is 1.55 μm. And its equivalent refractive index is 4.227. Below the p ^-- Si layer 20, the BOX layer 12 is formed of SiO ₂ , and the p ^-- Si layer 20 and the i-Ge layer 30 are formed of SiO ₂ having a refractive index of 1.444. It is covered by the cladding layer 50. Therefore, the BOX layer 12 and the cladding layer 50 are cladding. Assuming that the width W of the i-Ge layer 30 that absorbs light in the detector section is, for example, 6.0 μm, the effective width W _e of the MMI waveguide is 6.01 μm, and the beat length L _π is , 131.55 μm. For this reason, the position where two images are formed is a position 49.33 μm away from the input optical waveguide 60 according to the equation shown in Equation 1.

  Therefore, in order to form two images on the left and right of the input optical waveguide 60 connected to the central portion on one side 30a of the detector unit on which light is incident, half of 49.33 μm from the input optical waveguide 60 The reflective film 71 may be formed at a position 24.66 μm away from That is, the length L from one side 30a to the other side 30b of the i-Ge layer 30 to be a detector may be 24.66 μm.

As a result, the signal light is reflected by the reflective film 71 and propagates a total of 49.33 μm in the detector, and an image can be formed on one side 30 a of the detector to which the input optical waveguide 60 is connected. At this time, the images to be formed are formed on the one side 30a of the detector at positions of ± MMI _e / 6 from the center.

  Although the case where two images are formed has been described above, for example, four images may be formed. In this case, since the distance to the image forming position can be shortened, there is an advantage that the optical semiconductor device can be further miniaturized, but since the distance between the image forming position by the reflected light and the input optical waveguide 60 becomes short, the input There is a possibility that the reflected light may easily enter the optical waveguide 60.

  In the present embodiment, the signal light input from one side 30a of the detector unit is reflected by the reflective film 71 formed on the other side 30b of the detector unit, so that the effective propagation length can be obtained in the detector unit. And can obtain sufficient light absorption. Further, the light reflected by the reflection film 71 is focused on an area different from the area where the input optical waveguide 60 is formed on one side 30a of the detector section, and therefore the light returned to the input optical waveguide 60 Can be prevented from entering.

In the optical semiconductor device according to the present embodiment, when the size of the n-side electrode 41 is substantially the same as the size of the i-Ge layer 30, the width W is about 6.0 μm and the length L is about 24. The area is 66 μm, and the area on which the n-side electrode 41 is formed is about 148 μm ² . On the other hand, the n-side electrode 941 having the structure shown in FIG. 1 is formed so that the length in the longitudinal direction is about 30 μm and the length in the lateral direction is about 10 μm. The area to be formed is about 300 μm ² . Therefore, in the optical semiconductor device according to the present embodiment, the area where the n-side electrode is formed can be 1⁄2 or less as compared with the photodetector shown in FIG. As described above, since the capacitance can be reduced by narrowing the area in which the n-side electrode is formed, the responsiveness can be improved, and high-speed response can be coped with.

(Method of manufacturing optical semiconductor device)
Next, a method of manufacturing the optical semiconductor device according to the present embodiment will be described. The optical semiconductor element in the present embodiment is manufactured using the SOI substrate 10 shown in FIG. In the SOI substrate 10, a BOX layer 12 with a thickness of 3.0 μm and a p ⁻ -Si layer 20 with a thickness of 0.3 μm are sequentially stacked on a Si substrate 11. 5 (a) is a top view of the SOI substrate 10, and FIG. 5 (b) is a cross-sectional view taken along dashed dotted line 5A-5B in FIG. 5 (a).

Next, as shown in FIG. 6, ^p in the SOI substrate 10 - to form the input optical waveguide 60 by -Si layer 20, ^p regions the optical semiconductor element is formed in this embodiment - -Si layer 20 Do processing that leaves. Specifically, a photoresist is applied on the p ⁻ -Si layer 20 of the SOI substrate 10, and exposure and development are performed by an EB exposure apparatus to form a resist pattern (not shown). A resist pattern (not shown) is formed on the region where the input optical waveguide 60 is formed and the region where the p ⁻ -Si layer 20 of the optical semiconductor device in the present embodiment is formed. Thereafter, the p ⁻ -Si layer 20 in the region where the resist pattern is not formed is removed by ICP (Inductively Coupled Plasma) dry etching. ^Thus, p - to form a input optical waveguide 60 by -Si layer 20, ^p of the optical semiconductor device of the present embodiment - -Si layer 20 is formed. After this, the resist pattern (not shown) is removed by O ₂ ashing or the like. 6 (a) is a top view in this step, FIG. 6 (b) is a cross-sectional view cut along dashed dotted line 6A-6B in FIG. 6 (a), and FIG. 6 (c) is It is sectional drawing cut | disconnected in dashed-dotted line 6C-6D in Fig.6 (a).

Next, as shown in FIG. 7, boron (B: Boron) is ion-implanted in a part of the p ⁻ -Si layer 20 of the optical semiconductor device according to the present embodiment to form a p-Si region 21. The p-Si region 21 is formed from the region where the i-Ge layer 30 is formed in the optical semiconductor device according to the present embodiment to the region where the p-side electrode 42 is formed. Specifically, p ^- on the -Si layer 20, a photoresist is applied, exposed to i-line exposure apparatus, by performing development, not shown having an opening in a region where p-Si region 21 is formed Form a resist pattern of Thereafter, for example, ion implantation of B is performed under the conditions of a dose amount of 6.0 × 10 ¹⁴ cm ⁻² and an implantation energy of 30 keV. Thereafter, after removing a resist pattern (not shown) by O ₂ ashing or the like, the annealing treatment is performed for 5 seconds at a temperature of about 1000 ° C. by an annealing apparatus to activate B ions, whereby the p-Si region 21 is obtained. Form In the present embodiment, the p-Si region 21 is formed to have a carrier concentration of about 1.0 × 10 ¹⁹ cm ^−3, and, for example, the width Wa is about 23.0 μm and the length La is about 30. It is formed to have a thickness of 0.1 μm. 7 (a) is a top view in this step, and FIG. 7 (b) is a cross-sectional view taken along a dashed dotted line 7A-7B in FIG. 7 (a).

Next, as shown in FIG. 8, an SiO ₂ mask 81 having an opening 81 a is formed in the region where the i-Ge layer 30 is to be formed. Specifically, a SiO ₂ film is formed on the exposed p-Si region 21, the p ⁻ -Si layer 20, and the BOX layer 12 by LP-CVD (Low Pressure Chemical Vapor Deposition). Thereafter, a photoresist is applied on the formed SiO ₂ film, exposed and developed by an i-line exposure device, and an opening is not shown in the region where the i-Ge layer 30 is to be formed. Form a resist pattern. Thereafter, the SiO ₂ film in the region where the resist pattern is not formed is removed by ICP dry etching, and then the unshown resist pattern is removed by O ₂ ashing. Thus, a SiO ₂ mask 81 having an opening 81 a is formed in the region where the i-Ge layer 30 is to be formed. The opening 81 a of the SiO ₂ mask 81 thus formed has a width Wb of about 6.0 μm and a length Lb of about 30.0 μm. 8 (a) is a top view in this step, and FIG. 8 (b) is a cross-sectional view taken along a dashed dotted line 8A-8B in FIG. 8 (a).

Next, as shown in FIG. 9, the i-Ge layer 30 is epitaxially grown on the p-Si region 21 exposed in the opening 81 a of the SiO ₂ mask 81 by LP-CVD. Specifically, the SOI substrate on which the SiO ₂ mask 81 is formed is placed in the growth chamber of the LP-CVD apparatus, heated to a temperature of 900 ° C. in a H ₂ atmosphere by a lamp heater, and then this temperature is 5 By holding for a minute, the O ₂ adsorbed on the surface is removed. After this, the temperature is lowered to a temperature of 650 ° C., GeH ₄ is supplied into the growth chamber of the LP-CVD apparatus, and i is exposed on the exposed p-Si region 21 at the opening 81 a of the SiO ₂ mask 81 Grow the Ge layer 30; The growth conditions of the i-Ge layer 30 are as follows: the pressure in the growth chamber of the LP-CVD apparatus is 10 Torr, the supply amount of GeH ₄ is 20 ccm, the supply amount of H ₂ carrier gas is 10 ccm, and the growth time is 35 minutes. The growth rate of the i-Ge layer 30 under this condition is about 30 nm / min, and the film thickness of the i-Ge layer 30 to be formed is about 1000 nm. 9 (a) is a top view in this step, and FIG. 9 (b) is a cross-sectional view taken along the alternate long and short dash line 9A-9B in FIG. 9 (a).

Next, as shown in FIG. 10, in the upper part of the i-Ge layer 30, phosphorous (Phosphorus: P) is ion-implanted to form an n-Ge region 31. Specifically, the SOI substrate on which the i-Ge layer 30 is formed is taken out from the chamber of the LP-CVD apparatus, a photoresist is applied to the side on which the i-Ge layer 30 is formed, and an i-line exposure apparatus Exposure and development are performed. Thereby, a resist pattern (not shown) having an opening in a region where the n-Ge region 31 is formed is formed. Thereafter, for example, ion implantation of P is performed under the conditions of a dose amount of 6.0 × 10 ¹⁴ cm ⁻² and an implantation energy of 30 keV. Thereafter, after removing a resist pattern (not shown) by O ₂ ashing, the substrate is placed in an annealing apparatus, and annealing treatment is performed at a temperature of about 700 ° C. for 5 seconds to activate P ions, thereby n-Ge region. Form 31 In the present embodiment, n-Ge region 31 is formed to have a carrier concentration of approximately 1.0 × 10 ¹⁹ cm ⁻³ , and, for example, width Wc is approximately 5.0 μm, and length Lc is approximately It is formed to be about 30.0 μm. 10 (a) is a top view in this step, and FIG. 10 (b) is a cross-sectional view taken along dashed dotted line 10A-10B in FIG. 10 (a).

  Next, as shown in FIG. 11, a resist pattern 82 for forming an end face 70 of the other side 30b to be a reflection surface of the detector portion is formed. Specifically, a photoresist is applied to the surface on which the n-Ge region 31 is formed, and exposure and development are performed by an i-line exposure device to form an input optical waveguide 60 and a region where the detector portion is formed. A resist pattern (not shown) is formed on the top. As a result, a resist pattern 82 is formed on the region where the length Ld from the end of one side 30a of the detector section to which the input optical waveguide 60 and the input optical waveguide 60 are connected is up to about 24.66 μm. . 11 (a) is a top view in this step, and FIG. 11 (b) is a cross-sectional view cut along the dashed dotted line 11A-11B in FIG. 11 (a).

Next, as shown in FIG. 12, using the resist pattern 82 as a mask, the n-Ge region 31, the i-Ge layer 30, the p-Si region 21, the p ⁻ -Si layer 20, the BOX layer 12, the Si substrate 11. An end surface 70 is formed by removing a part by dry etching. In this way, the end face 70 is formed on the other side 30 b of the detector section. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. FIG. 12 (a) is a top view in this step, and FIG. 12 (b) is a cross-sectional view taken along dashed dotted line 12A-12B in FIG. 12 (a).

Next, as shown in FIG. 13, a dielectric multilayer film is formed by EB (electron beam) evaporation to form a reflective film 71a. The reflective film 71a is formed by alternately forming four pairs of SiO ₂ films having a thickness of 268.35 nm and Si films having a thickness of 111.51 nm on the end face 70. The dielectric multilayer film is formed to have the above film thickness in the light traveling direction. 13 (a) is a top view in this step, and FIG. 13 (b) is a cross-sectional view taken along the alternate long and short dash line 13A-13B in FIG. 13 (a).

Next, as shown in FIG. 14, the reflection film 71 a formed in the end surface 70 and the area other than the vicinity of the end surface 70 is removed, and the reflection film 71 is formed only in the area near the end surface 70 and the end surface 70. . Specifically, a photoresist is applied on the surface on which the reflective film 71a is formed, and exposure and development are performed by the i-line exposure device, whereby the reflective film 71 in the vicinity of the end surface 70 and the end surface 70 is formed. A resist pattern (not shown) is formed on the region. Thereafter, the reflective film 71a in the region where the resist pattern is not formed is removed by ICP dry etching to form the reflective film 71 only in the end surface 70 and the region in the vicinity of the end surface 70. The reflective film 71 formed in this manner has a high reflectance for light having a wavelength of 1.55 μm, which is signal light. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. FIG. 14 (a) is a top view in this step, and FIG. 14 (b) is a cross-sectional view taken along dashed dotted line 14A-14B in FIG. 14 (a).

Next, as shown in FIG. 15, a cladding layer 50 is formed on the side surface and the upper surface of the i-Ge layer 30, and on the upper surfaces of the p-Si region 21 and the p ⁻ -Si layer 20. Contact holes 50a and 50b for forming the electrode 41 and the p-side electrode 42 are formed. Specifically, the cladding layer 50 is formed by depositing a SiO ₂ film having a thickness of about 1000 nm by plasma CVD. Thereafter, a photoresist is applied on the formed cladding layer 50, exposed and developed by an i-line exposure device, and a resist (not shown) having an opening in a region where the contact holes 50a and 50b are to be formed. Form a pattern. After that, the contact holes 50a and 50b are formed by removing the cladding layer 50 in the region where the resist pattern is not formed by ICP dry etching. The contact hole 50a thus formed is formed in a substantially rectangular shape having a width We of about 5.0 μm and a length Le of about 24.0 μm, and the surface of the n-Ge region 31 is formed on the bottom surface Is exposed. Contact hole 50b is formed on both sides of contact hole 50a so as to have a substantially rectangular shape with a width Wf of about 4.0 μm and a length Le of about 24.0 μm. The surface of the region 21 is exposed. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. 15 (a) is a top view in this step, and FIG. 15 (b) is a cross-sectional view taken along the alternate long and short dash line 15A-15B in FIG. 15 (a).

Next, as shown in FIG. 16, the n-side electrode 41 is formed in the contact hole 50a, and the p-side electrode 42 is formed in the contact hole 50b. Specifically, an Al film having a thickness of about 500 nm is formed on the cladding layer 50 in which the contact holes 50a and 50b are formed by sputtering. Thereafter, a photoresist is applied on the formed Al film, exposed and developed by an i-line exposure device, and not shown in the region where the n-side electrode 41 and the p-side electrode 42 are formed. Form a resist pattern. Thereafter, the n-side electrode 41 and the p-side electrode 42 are formed by removing the Al film in the region where the resist pattern is not formed by dry etching. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. 16 (a) is a top view in this step, FIG. 16 (b) is a cross-sectional view cut along the dashed dotted line 16A-16B in FIG. 16 (a), and FIG. 16 (c) is It is sectional drawing cut | disconnected in dashed-dotted line 16C-16D in Fig.16 (a).

  The optical semiconductor element in this embodiment can be manufactured by the above steps.

Although the case where the SOI substrate is used as the substrate has been described in the present embodiment, a substrate in which a nitride film is formed on a Si substrate may be used. In addition, although the case where the photo detector portion is formed of Ge has been described, it may be formed of SiGe or the like besides Ge. In addition, although the reflective film 71 has been described as a dielectric multilayer film formed of SiO ₂ and Si, it may be a dielectric multilayer film in which other dielectric materials are combined, and further, light may be It may be a reflective metal film or the like. In addition, the substrate, the photodetector unit, the optical waveguide and the like may be formed of a material such as InP or GaAs. The n-side electrode 41 and the p-side electrode 42 may be formed of Cu, Au or the like. Further, if desired characteristics can be obtained with respect to the width of the input optical waveguide 60, the width of the photodetector portion, etc., the input optical waveguide 60 can be freely designed, and the input optical waveguide 60 is formed to have a tapered structure. It is also good.

  Further, the image forming position of the image by the light reflected by the reflection film 71 may not necessarily be the end face of one side 30 a of the detector portion, and the light reflected by the reflection film 71 to the input optical waveguide 60 is returned as return light If not incident, the imaging position may be slightly shifted. Further, in the present embodiment, the case where two images are formed by the reflected light on one side 30a of the detector unit has been described, but four images may be formed.

Second Embodiment
Next, a second embodiment will be described. The optical semiconductor element in the present embodiment is an optical semiconductor element having a structure in which reflection films are formed on both sides of the input optical waveguide also on one side of the detector section.

FIG. 17 shows the structure of the optical semiconductor element according to the present embodiment. In the optical semiconductor device according to the present embodiment, the n-Ge region 31, the i-Ge layer 30, the p-Si region 21, the p ^-- Si layer 20, the BOX layer 12, and the Si are also provided on one side 30a of the detector portion. An end face 170 is formed by removing a part of the substrate 11 by dry etching or the like. The end surface 170 is formed in a region excluding the region to which the input optical waveguide 60 is connected, and a reflective film 171 is formed by forming a dielectric multilayer film so as to cover the formed end surface 170. There is. As in the first embodiment, an end surface 70 is formed on the other side 30 b of the detector unit, and a reflective film 71 is formed to cover the end surface 70.

  In the present embodiment, light incident on one side 30a from the input optical waveguide 60 to the detector portion is reflected by the reflective film 71 on the other side 30b of the detector portion and reaches the one side 30a without being completely attenuated. Even in this case, the light is reflected by the reflection film 171. As described above, the light reflected by the reflective film 171 is returned to the inside of the detector portion, so that the light absorption in the i-Ge layer 30 can be enhanced. Further, when the reflective film 171 is not formed, the reflected light reflected by the reflective film 71 is scattered or the like on one side 30 a of the detector section, which may cause stray light or cause noise or the like. There is. In the optical semiconductor device according to the present embodiment, since the reflective film 171 is formed on one side 30a of the detector, generation of stray light can be prevented, and noise can be suppressed.

(Method of manufacturing optical semiconductor device)
Next, a method of manufacturing the optical semiconductor device according to the present embodiment will be described. The manufacturing method of the optical semiconductor device in the present embodiment is the same as the first embodiment in the steps from FIG. 5 to FIG. 10, and the steps after FIG. 10 will be described based on FIG. .

  After the process shown in FIG. 10, as shown in FIG. 18, a resist pattern 182 is formed for forming the end face 70 on the other side 30b and the end face 170 on one side 30a which will be the reflection surface of the detector. Specifically, a photoresist is applied to the surface on which the n-Ge region 31 is formed, and exposure and development are performed by an i-line exposure device to form an input optical waveguide 60 and a region where the detector portion is formed. A resist pattern (not shown) is formed on the top. Thereby, a resist pattern 82 is formed on the region where the length Lg from one side 30a to the other side 30b to which the input optical waveguide 60 and the input optical waveguide 60 are connected is about 24.66 μm. FIG. 18 (a) is a top view in this step, and FIG. 18 (b) is a cross-sectional view taken along dashed dotted line 18A-18B in FIG. 18 (a).

Next, as shown in FIG. 19, using the resist pattern 182 as a mask, the n-Ge region 31, the i-Ge layer 30, the p-Si region 21, the p ⁻ -Si layer 20, the BOX layer 12, and the Si substrate 11. An end face 70, 170 is formed by removing a part by dry etching. As a result, the end face 70 is formed on the other side 30 b of the detector portion, and the end face 70 is formed on the one side 30 a of the detector portion except the region to which the input optical waveguide 60 is connected. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. 19 (a) is a top view in this step, and FIG. 19 (b) is a cross-sectional view taken along the alternate long and short dash line 19A-19B in FIG. 19 (a).

Next, as shown in FIG. 20, a dielectric multilayer film is formed by EB evaporation to form a reflective film 171a. The reflective film 171a is formed by alternately forming four pairs of SiO ₂ films having a film thickness of 268.35 nm and Si films having a film thickness of 111.51 nm on the end faces 70 and 170. FIG. 20 (a) is a top view in this step, and FIG. 20 (b) is a cross-sectional view taken along alternate long and short dash line 20A-20B in FIG. 20 (a).

Next, as shown in FIG. 21, the reflecting film 171a formed in the vicinity of the end face 70 and the end face 70 and in the area other than the end face 170 and the vicinity of the end face 170 is removed. Thus, the reflective film 71 is formed in the end face 70 and the area near the end face 70, and the reflective film 171 is formed in the area near the end face 170 and the end face 170. Specifically, a photoresist is applied to the surface on which the reflective film 171a is formed, and exposure and development are performed by an i-line exposure device. Thus, a resist pattern (not shown) is formed on the end face 70 and the area where the reflective film 71 is formed in the vicinity of the end face 70 and the area where the end film 170 and the reflection film 171 near the end face 170 are formed. After that, the reflective film 171 is removed by ICP dry etching in the region where the resist pattern is not formed, thereby forming the reflective film 71 in the region near the end surface 70 and the end surface 70. The reflective film 171 is formed in the region. The reflective film 171 is formed in an area excluding the area where the input optical waveguide 60 is connected on one side 30 a of the detector section. The reflective films 71 and 171 formed in this manner have high reflectance with respect to light having a wavelength of 1.55 μm which becomes signal light. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. 21 (a) is a top view in this step, and FIG. 21 (b) is a cross-sectional view taken along dashed dotted line 21A-21B in FIG. 21 (a).

Next, as shown in FIG. 22, a cladding layer 50 is formed on the side surface and the upper surface of the i-Ge layer 30, and the upper surfaces of the p-Si region 21 and the p ⁻ -Si layer 20. Contact holes 50a and 50b for forming the electrode 41 and the p-side electrode 42 are formed. Specifically, the cladding layer 50 is formed by depositing a SiO ₂ film having a thickness of about 1000 nm by plasma CVD. Thereafter, a photoresist is applied on the formed cladding layer 50, exposed and developed by an i-line exposure device, and a resist (not shown) having an opening in a region where the contact holes 50a and 50b are to be formed. Form a pattern. After that, the contact holes 50a and 50b are formed by removing the cladding layer 50 in the region where the resist pattern is not formed by ICP dry etching. The contact hole 50a thus formed is formed in a substantially rectangular shape having a width We of about 5.0 μm and a length Le of about 24.0 μm, and the surface of the n-Ge region 31 is formed on the bottom surface Is exposed. Contact hole 50b is formed on both sides of contact hole 50a so as to have a substantially rectangular shape with a width Wf of about 4.0 μm and a length Le of about 24.0 μm. The surface of the region 21 is exposed. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. FIG. 22 (a) is a top view in this step, and FIG. 22 (b) is a cross-sectional view taken along dashed dotted line 22A-22B in FIG. 22 (a).

Next, as shown in FIG. 23, the n-side electrode 41 is formed in the contact hole 50a, and the p-side electrode 42 is formed in the contact hole 50b. Specifically, an Al film having a thickness of about 500 nm is formed on the cladding layer 50 in which the contact holes 50a and 50b are formed by sputtering. Thereafter, a photoresist is applied on the formed Al film, exposed and developed by an i-line exposure device, and not shown in the region where the n-side electrode 41 and the p-side electrode 42 are formed. Form a resist pattern. Thereafter, the n-side electrode 41 and the p-side electrode 42 are formed by removing the Al film in the region where the resist pattern is not formed by dry etching. Thereafter, the resist pattern (not shown) is removed by O ₂ ashing. 23 (a) is a top view in this step, FIG. 23 (b) is a cross-sectional view cut along the dashed dotted line 23A-23B in FIG. 23 (a), and FIG. 23 (c) is It is sectional drawing cut | disconnected in the dashed-dotted line 23C-23D in Fig.23 (a).

  The optical semiconductor element in this embodiment can be manufactured by the above steps.

  The contents other than the above are the same as in the first embodiment.

  As mentioned above, although an embodiment was explained in full detail, it is not limited to a specific embodiment, and various modification and change are possible within the limits indicated in a claim.

Further, the following appendices will be disclosed in connection with the above description.
(Supplementary Note 1)
An input optical waveguide formed on a substrate,
A detector section to which the input optical waveguide is connected on one side;
A reflective film formed on an end face of the other side opposite to the one side in the detector section;
Have
The detector detects light input from the input optical waveguide, and
A light semiconductor device characterized in that light input to one side of the detector section from the input optical waveguide is reflected by the reflection film formed on the end face of the other side.
(Supplementary Note 2)
The optical semiconductor device according to claim 1, wherein the light reflected by the reflection film forms an image on an area different from an area connected to the input optical waveguide on the one side.
(Supplementary Note 3)
The input optical waveguide is connected to a central portion on one side of the detector unit,
The light according to claim 2, wherein the light reflected by the reflection film forms an image on each side of the area where the input optical waveguide is connected on one side of the detector unit. Semiconductor device.
(Supplementary Note 4)
On one side of the detector section, an end surface on one side is formed on both sides of the area where the input optical waveguide is connected,
The optical semiconductor device according to any one of appendices 1 to 3, wherein a reflection film is formed on an end face on one side of the detector unit.
(Supplementary Note 5)
The substrate is made of silicon,
A silicon oxide film is formed on the substrate,
The input optical waveguide and the detector section are formed on the silicon oxide film,
The input optical waveguide is formed of a silicon layer,
The detector section is formed by stacking a silicon layer and a layer formed of a material containing germanium on the silicon layer,
11. The optical semiconductor device according to any one of appendices 1 to 4, wherein the input optical waveguide is connected to a silicon layer in the detector unit.
(Supplementary Note 6)
The optical semiconductor device according to claim 5, wherein the end face is formed by removing the layer formed of the material containing germanium by dry etching.
(Appendix 7)
A first conductivity type region doped with an impurity element of a first conductivity type is formed in the silicon layer, and a part of the first conductivity type region is made of a material including germanium. The formed layer is formed,
A second conductivity type region doped with an impurity element of a second conductivity type is formed on the layer formed of the material containing germanium on the upper surface of the layer formed of the material containing germanium,
One electrode is formed on the second conductivity type region,
The detector portion is formed of a part of the first conductivity type region, a layer formed of a material containing the germanium, and the second conductivity type region.
The other electrode is formed in a region where the layer formed of the material containing germanium is not formed on the first conductivity type region. Optical semiconductor device.
(Supplementary Note 8)
The optical semiconductor device according to any one of appendices 1 to 7, wherein the reflection film is formed of any one of a dielectric multilayer film, a metal film, and a multilayer film formed of a dielectric and a semiconductor.

10 SOI substrate 11 Si substrate 12 BOX layer 20 ^p - -Si layer 21 p-Si region 30 i-Ge layer other side 31 of the one side 30b detector portion of 30a detector unit n-Ge region 41 n-side electrode 42 p Side electrode 50 clad layer 60 input optical waveguide 70 end face 71 reflection film

Claims (6)

An input optical waveguide formed on a substrate,
A detector section to which the input optical waveguide is connected on one side;
A reflective film formed on an end face of the other side opposite to the one side in the detector section;
Have
The detector detects light input from the input optical waveguide, and
The input optical waveguide is connected to a central portion on one side of the detector unit,
The light input from the input optical waveguide to one side of the detector unit is reflected by the reflection film formed on the end face on the other side, and the input optical waveguide is reflected on one side of the detector unit. the optical semiconductor element characterized imaging to Rukoto each image on both sides of the area to which it is connected. An input optical waveguide formed on a substrate,
A detector section to which the input optical waveguide is connected on one side;
A reflective film formed on an end face of the other side opposite to the one side in the detector section;
Have
The detector detects light input from the input optical waveguide, and
The light input from the input optical waveguide to one side of the detector unit is reflected by the reflective film formed on the end surface on the other side,
On one side of the detector section, an end surface on one side is formed on both sides of the area where the input optical waveguide is connected,
An optical semiconductor device characterized in that a reflection film is formed on an end face on one side of the detector section. On one side of the detector section, an end surface on one side is formed on both sides of the area where the input optical waveguide is connected,
The end face of one side of the detector unit, an optical semiconductor device according to claim 1, wherein a reflection film is formed. The substrate is made of silicon,
A silicon oxide film is formed on the substrate,
The input optical waveguide and the detector section are formed on the silicon oxide film,
The input optical waveguide is formed of a silicon layer,
The detector section is formed by stacking a silicon layer and a layer formed of a material containing germanium on the silicon layer,
The optical semiconductor device according to any one of claims 1 to 3 , wherein the input optical waveguide is connected to a silicon layer in the detector unit. A first conductivity type region doped with an impurity element of a first conductivity type is formed in the silicon layer, and a part of the first conductivity type region is made of a material including germanium. The formed layer is formed,
A second conductivity type region doped with an impurity element of a second conductivity type is formed on the layer formed of the material containing germanium on the upper surface of the layer formed of the material containing germanium,
One electrode is formed on the second conductivity type region,
The detector portion is formed of a part of the first conductivity type region, a layer formed of a material containing the germanium, and the second conductivity type region.
5. The light according to claim 4 , wherein the other electrode is formed in a region where the layer made of the material containing germanium is not formed on the first conductivity type region. Semiconductor device. The optical semiconductor device according to any one of claims 1 to 5 , wherein the reflection film is formed of any one of a dielectric multilayer film, a metal film, and a multilayer film formed of a dielectric and a semiconductor. .

Images